Two wire load measuring system



June 10, 1952 R. e. LOCKETT TWO WIRE LOAD MEASURING SYSTEM Filed Jan.28, 1948 INVENTOR. m 6.1001977 Patented June 10, 1952 UNITED STATESPATENT OFFICE TWO WIRE LOAD MEASURING SYSTEM Ralph G. Lockett, Narbeth,Pa., assignor to ITE Circuit Breaker Company, Philadelphia, Pa., acorporation of Pennsylvania Application January 28, 1948, Serial No.4,833

2 Claims. (01. 175294) I 2 My invention relates to a novel two wire loadResistors 6 and I are thereupon connected in measuring system for directcurrent circuit, and circuit across the contacts of the circuit breakermore particularly relates to load measuring sys- I in amanner to bedescribed hereinafter, and tems for use in ungrounded systems. measurethe fault. Should the fault have cleared In many industrial systems, thereturn circuit itself, the circuit breaker I is reclosed. The opfor thetrolley is usually preferably ungrounded. erations for the above arewell known in the art When a fault occurs it has heretofore been the andwill be briefly described in connection with practice to close ameasuring resistance circuit my novel addition thereto. across theterminals of the open circuited circuit In accordance with the presentinvention, a breaker by which the extent of the fault is 10 circuitinterrupter 8 is connected in the return measured. If the fault hasautomatically circuit II and provided with a closing magnet 9. cleareditself, the circuit breaker is automatically In the event of a doublefault to ground circuit reclosed. interrupter 8 is provided with a faultcurrent Opening the positive side by a single pole responsive magnet 5,which will cause the circuit breaker, however, leaves the negative orun- 16 interruptor 8 to open and disconnect the return grounded sidestill with a high and dangerous conductor II from the source of power.The

potential. For example, an operator may have circuit arrangement as willbe described hereaccidentally thrown some tool, such as a wrench,inafter is such that upon the interruption of the across the trolley andreturn circuit. In order circuit breaker I the circuit interruptor 8 isto assist such an operator in clearing himself 20 momentarily opened;thus by reason of the disfrom contact with such a fault, it is desirableconnection of both the circuit breaker I and cirthat both the return andthe trolley circuit be cuit breaker 8 both the conductor 2 and thereopened. That is to say, it is often essential that turn circuit II areopened.

both sides of such a system be opened in response After an interval oftime, as will be described to a fault. After a predetermined interval ofhereinafter, the circuit interruptor 8 is reclosed time the returncircuit should be reclosed for the and the resistors 6 and I are then incircuit for purpose of measuring the extent of the fault measuring thefault to determine whether the in order to control the reclosing of thecircuit. circuit breaker I is to reclose.

Accordingly an object of my invention is to The above operations willnow be described provide a novel circuit arrangement whereby in detail.Normally with the circuit breaker I both sides of an ungrounded circuitare momenand the circuit breaker 8 closed, the circuit extarily openedfollowing a fault. tends over the conductor 2 and through the fault Afurther object of my invention is to provide responsive relay 3, circuitthrough the contacts a novel circuit arrangement for measuring the ofcircuit breaker I and through load I 0 over extent of a fault. thecontacts of the circuit breaker 8 through Still another object of myinvention is to prothe current responsive relay 5 and over the returnvide a novel circuit arrangement for two single circuit II to thesource. pole circuit breakers in which both the trolley It will beassumed that a fault current enerand the return circuit are opened inresponse to gizes the relay 3 to effect interruption of the faults.circuit breaker contacts I. With the circuit These and other objects ofmy invention will breaker closed, an energizing circuit was combe moreclearly apparent in the detailed descrippleted for the holding winding 9of the circuit tion of the invention which is to follow in conbreaker 8,the circuit extending from the source nection with the accompanyingdrawing which and through the circuit breaker I over contactschematically shows one circuit arrangement for I3 through the fuse I'Iover contact Ial, an

carrying out my invention. auxiliary contact on the circuit breakerwhich Referring now to the drawing, the circuit is closed when thecircuit breaker is closed and breaker I of the type illustrated inPatent No. which opens when the circuit breaker opens,

1,695,506, is connected in the conductor 2 and through the resistor I8and the holding magnet provided with fault current responsive magnetwinding 9 to the return circuit I I. Upon the 3. In the event of a faultas indicated at the opening of the circuit breaker I, contact IaI dottedline, the circuit breaker I is automatically opens, thus opening theenergizing circuit for operated to disconnect its contacts and open thethe closing magnet 9 of the circuit breaker 8 circuit of the conductor 2from the source of and the circuit breaker 8 thereupon opens.

power. The contact Ibl, which is an auxiliary contact on the circuitbreaker I is open while the circuit breaker I is closed and is closed bythe opening of the circuit breaker I, and a circuit is now completedfrom the source over th conductor 2, through the winding 3 over thecontacts I2 and fuse I 4, through the contact IbI over the resistor I5through the winding I6 to the return circuit II. I

The contact Ibl is also an auxiliary contact which has a time delayattachment thereto for delaying its closing for an interval of timeafter the circuit breaker I has opened. Accordingly this circuit willnot be closed for a predetermined interval of time after the circuitbreaker I has opened and during this interval the circuit breaker 8stays open.

After this predetermined interval, however, the energizing circuit forthe winding I6 is completed and this relay [6 is energized to close itscontacts I6aI and I6a2. The relay I6 is provided with a special set ofcontacts I6a3 which are also closed upon the energization of the relayl6. Closing of the contacts I6a3 now completes an energizing circuitfrom the conductor 2 over the contacts M3 and through the closed contact8b, which is closed while the closingmagnet 9 is deenergized, andthrough the winding 9 to the return circuit II.

Energization of the closing magnet 9 will now reclose the circuitbreaker 8. Upon its closing, contact 8b opens, but the circuit nowcontinues through the current reducing resistor I8 to hold this winding9 energized. With the circuit breaker 8 thus reclosed, the circuit is incondition for measuring the fault. This measuring circuit now extendsfrom the conductor 2 and over the contacts I2 and [Gal through resistors6 and I through contact IBM and contact I3 through the fault to circuitinterrupter 8 and current responsive relay 5 on conductor II to thesource.

The mid-point between resistors 6-and I is connected through resistor 2|to the load measuring closing coil 24.

If, as is well known inthe art now, the fault has cleared itself whenthe above described circuit is completed, sufficient current from thesource will flow through the winding of the load measuring coil 24 toenergize this relay. Load measuring relay 24 comprises the winding 24and the holding coil 25, as described in Patent No. 1,498,695.

Upon energization of'the winding 24, its associated armature is operatedto close its contact 240, and an obvious energizing circuit i nowcompleted for the closing control relay 22. Energization of relay 22closes-its'contacts 22aI and 22112 and an obvious energizing circuit isnow completed through the contact Set on the de-energized trip coil 3and through contacts 22aI and 22:12, and through the winding of thecircuit breaker closing coil 23.

Energization of the circuit breaker closing coil 23 will operate thecircuit breaker I to reclose in a manner 'now well known in the art.Upon reclosing of the circuit breaker I, contact Ibl will open,effecting a de-energization of the resistor control relay I6 andits'contacts MI, I M2 and I6a3 will open, thus resulting in thedeenergization of both the closing and holding windings 24 and 25,respectively.

The opening of contact lbI also opens the energizing circuit for theclosing coil control relay 22 which in turn opens the 22aI and 22a2.Upon the opening of these contacts the circuit coning coil 23 to effecta reclosing of the circuit breaker I.

In the foregoing I have described my invention solely inconnection withspecific illustrative embodiments thereof. Since many variations andmodifications of my invention will now be obvious to those skilled inthe art, I prefer to be bound not by the specific disclosures hereincontained, but only by the appended claims.

I claim:

1. In an ungrounded direct current system having a first conductor and areturn conductor, and load measuring relays and resistors; a firstreclosing circuit breaker having engaging contacts connected in seriesin said first conductor an auxiliary contact on said circuit breakerclosed when said first circuit breaker is closed and open when saidfirst circuit breaker is open, a first reclosing magnet for said firstcircuit breaker operative when energized for reclosing and holdingclosed said contacts of said first circuit breaker, and operative whendeenergized for effecting disengagement of said contacts of said firstcircuit breaker, a first trip magnet means for said first circuitbreaker responsive to a fault current in said first circuit breaker toeffect deenergization of said first reclosing magnet; a second reclosingcircuit breaker having engaging contacts connected in series in saidreturn conductor, a second reclosing magnet for said second circuitbreaker operative, when energized, for reclosing and holding closed saidcontacts of said second circuit breaker and operative when deenergized,for effecting disengagement of said contacts of said second circuitbreaker said auxiliary contact providing an energizing circuit for saidsecond reclosing magnet when said first circuit breaker is closedand'opening said energizing circuit when said first circuit breaker isopened, a second trip magnet, said second trip magnet being connected inseries in said return conductor and including means responsive to afault current in said second circuit breaker for opening the energizingcircuit of said first reclosing magnet to effect de-energization of saidfirst reclosing magnet, a relay, a time delay contact on said firstcircuit breaker which closes an energizing circuit for said relay apredetermined time after said first circuit breaker opens, circuit meanscontrolled by said energized relay for completing a secondenergizingcircuit for said second reclosing magnet, circuit connections includingsaid load measuring resistors and relays operative following the closingof said second circuit breaker for testing the fault condition of saiddirect current system while said first circuit breaker is in the contactdisengaged position and relay means operative in the event said fault ontest is found to have been cleared for energizing said first reclosingmagnet to reclose said first circuit breaker; said first and secondcircuit breakers providing isolation for line to line and double line toground faults.

2. In an ungrounded direct current system having a first conductor and areturn conductor, and load measuring relays and resistors; a firstreclosing circuit breaker having engaging contacts connected in seriesin said first conductor, a first reclosing magnet for said first circuitbreaker for effecting, when energized, reclosing and holding closed saidcontacts of said first circuit breaker and for efiecting whende-energized, disengagement of said contacts of said first circuitbreaker, a first trip magnet connected in series in said first conductorfor said first circuit breaker responsive to a fault current in saidfirst circuit breaker to effect de-energization of said first reclosingmagnet; a second reclosing circuit breaker having engaging contactsconnected in series in said return conductor, a second reclosing magnetfor said second circuit breaker for effecting, when energized, reclosingand holding closed said contacts of said second circuit breaker and forefiecting when de-energized, disengagement of said contacts of saidsecond circuit breaker, a second trip magnet, contacts of said secondtrip magnet being in series with the said contacts of said first tripmagnet, said second trip magnet connected in series in said returnconductor and responsive to a fault current in said second circuitbreaker to effect de-energization of said first reclosing magnet, arelay, a time delay contact on said first circuit breaker which closesthe energizing circuit for said relay a predetermined time after saidfirst circuit breaker opens, means including said load measuringresistors and relays for completing an energizing circuit for said firstreclosing magnet when said load measuring re- 6 sistor and relaysindicates that the fault which caused disengagement of said firstcircuit breaker has been cleared; an auxiliary contact on said firstcircuit breaker for completing an energizing circuit for said secondreclosing magnet, said auxiliary contact maintains said second circuitbreaker in the circuit closed position when said first circuit breakeris closed and maintaining said second circuit breaker open when saidfirst circuit breaker is opened, said relay when energized, completingan energizing circuit by-passing said auxiliary contact for said secondreclosing magnet, and also completing the energizing circuit for theload measuring resistors and relays; said load measuring relays whenenergized, completing an energizing circuit for said first reclosingmagnet, said first and second circuit breakers providing isolation forline to line and double line to ground faults.

RALPH G. LOCKETT.

REFERENCES CITED The following references are'of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,498,695 Ravey June 24, 19241,505,633 Finney Aug. 19, 1924 1,632,983 Proctor June 21, 1927 1,669,516Golladay May 15, 1928 1,695,506 Ravey Dec. 18, 1928 2,244,086 Scott June3, 1941 2,249,870 Taliaferro July 22, 1941

